1. Field of the Invention
The present invention relates to a positive photosensitive resin precursor composition suitably used for a surface protection layer and an insulating interlayer of a semiconductor element, an insulating layer of an organic electroluminescent device, and the like, and which becomes soluble in alkaline developers by being exposed to UV light.
2. Description of the Related Art
Known positive heat-resistant resin precursor compositions, whose exposed area is dissolved by development, may contain a polyamic acid and a quinone diazide; a soluble polyimide having a hydroxy group and a quinone diazide; or a polyamide having a hydroxy group and a quinone diazide.
Unfortunately, a typical positive heat-resistant resin precursor composition containing polyamic acid and quinone diazide hardly provides desired patterns because the carboxyl group of the polyamic acid has a solubility higher than the dissolution inhibition of the quinone diazide, in alkali. Although the positive heat-resistant resin precursor composition containing soluble polyimide whose principal chain has a hydroxy group reduces such a problem, the structure is disadvantageously limited to ensure solubility, and consequently the resulting polyimide resin is less solvent-resistant. The composition containing polyamide having a hydroxy group and quinone diazide is also limited in structure to ensure solubility. Consequently, the resulting resin, which is obtained by heat treatment, is undesirably less solvent-resistant.
In order to control the alkali solubility of the polyamic acid, a polyamic acid derivative has been developed whose carboxyl group is protected with an ester group. Compositions containing the polyamic acid derivative and naphthoquinone diazide extremely increase the dissolution inhibition of the naphthoquinone diazide in alkali. Consequently, while the compositions can provide desired patterns, the photosensitivity is largely degraded in most cases.
Some compositions providing an increased photosensitivity have recently been disclosed. For example, Japanese Unexamined Patent Application Publication No. 2002-328472 teaches a composition containing a polyamic ester and/or a polyamic polymer and a thermally cross-likable compound having a phenolic hydroxy group; Japanese Unexamined Patent Application Publication No. 2001-42527 and U.S. Pat. No. 6,329,110, a composition containing a polyamic ester and an iodonium salt as a dissolution inhibitor; Japanese Unexamined Patent Application Publication No. 2002-169283, a composition containing a polyamide and a iodonium salt as the dissolution inhibitor; Japanese Unexamined Patent Application Publication No. 2002-122993, a composition containing a polyamic ester, a photo acid generator, and a compound having a vinyloxy group; and U.S. Pat. No. 6,600,006, a composition containing a polyamic ester having an acid degradable group and a photo acid generator. These compositions provide desired photosensitivity as long as they are developed immediately after exposure. However, if the compositions are allowed to stand for a time interval of several hours to several days between exposure and development, the photosensitivity is extremely degraded.
In use of the heat-resistant resin precursor composition for semiconductor devices, the resulting cured resin by heating remains in the device as a permanent coating. Accordingly, the adhesion between the cured coating and the substrate is very important. However, the composition does not provide an adequate adhesion to the substrate, and accordingly it is unsuitable for practical use.
Hence, the above-described known compositions for enhancing the photosensitivity result in a degraded photosensitivity if they are allowed to stand for a time interval of several hours to several days between exposure and development, or do not ensure adequate adhesion to the substrate if they are applied to semiconductor devices, disadvantageously.